| 1/12/05 (VJC)
of new papers for Faculty 1000.
N Terminus of Bacterial Elongation Factor Tu Elicits Innate Immunity
in Arabidopsis Plants
The Plant Cell, Vol. 16, 3496–3507, December 2004
Gernot Kunze, Cyril Zipfel, Silke Robatzek, Karsten Niehaus, Thomas
Boller, and Georg Felixa
The work provides comprehensive and convincing evidence for the identification
of EF-Tu, a protein translation elongation factor, as a novel PAMP
(pathogen-associated molecular pattern) capable of triggering innate
immune responses and induced resistance in Arabidopsis plants. N-terminal
acetylation of the synthetic peptides corresponding to the N terminus
of EF-Tu exhibits potent activity to induce conserved defense responses.
The fact that EF-Tu represents particularly conserved structure of
a large class of microbes and was also observed to act as a stimulator
of a proinflammatory response in the presence of soluble CD14 in mammals
suggests the possibility that EF-Tu, similar to flagellin, might act
as a PAMP for the innate immune system of both animals and plants.
Phosphorylation of 1-Aminocyclopropane-1-Carboxylic
Acid Synthase by MPK6, a Stress-Responsive Mitogen-Activated Protein
Kinase, Induces Ethylene Biosynthesis in Arabidopsis.
The Plant Cell, Vol. 16, 3386–3399, December 2004
Yidong Liu and Shuqun Zhang
The finding reveals a novel mechanism responsible for the biosynthesis
control of the plant stress hormone ethylene by stress-activated MAPK
cascades. In a set of elegant experiments, the authors identified
selected isoforms of 1-aminocyclopropane-1-carboxylic acid synthase
(ACS2/6), the rate-limiting enzyme of ethylene biosynthesis, as substrates
of Arabidopsis MPK6. Activated MPK6 phosphorylates the unique C-terminal
tail of ACS2/6 to enhance protein stability and ethylene evolution.